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Doug Self Preamp from Linear Audio #5
Doug Self Preamp from Linear Audio #5
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Old 17th February 2021, 11:17 AM   #1601
mfwalker1 is offline mfwalker1  Australia
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Default Unbalaced inputs.

Quote:
Originally Posted by PRR View Post
> if I only wanted unbalanced inputs can I .....

?? That's like modifying TV's Batmobile into a Ford Galaxie. Take off a lot of fancy-stuff. Doug Self shows unbalanced inputs earlier in the book. While the book is copyrighted, this circuit and values are not critical or original. At "C", if input levels are huge, make R2 a pot; if signals are happy size but there is a need to fade to silence, make R4 a pot.
Yes, I get your point. I don't have a single balanced source (I do have a balanced power amp). Maybe this build is not for me. Perhaps the DS Precision Preamplifer is what I'm after. Wow that's an expensive PCB though...
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Old 18th February 2021, 03:52 AM   #1602
PRR is offline PRR  United States
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Doug Self Preamp from Linear Audio #5
Quote:
Originally Posted by diyralf View Post
C: As a general rule, attenuation should only take place on the volume control.
B: First attenuataion then amplification. Bad thing! Isn't it?
Quote:
Originally Posted by PRR View Post
.........if input levels are huge, make R2 a pot.....
Take it in context.
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Old 24th February 2021, 03:48 PM   #1603
ericoto is offline ericoto  United States
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Just completed this preamp working on getting panels cut Rather than reinvent Foes anyone have available .DXF files that can be used for front and back panels? I have tried to convert the .pdf files I have found on the site bug won’t convert. Any help appreciated
Thanks
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Old 7th March 2021, 02:23 PM   #1604
aniko71 is offline aniko71  Greece
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Quote:
Originally Posted by redjr View Post
Thanks. I'll check the thread. Parts came from Mouser.
In my last batch ordered from Mouser I had a 200K/3W resistor 1% Metal Oxide which I paid for 7,34 Euros ant it turned out to measure 32K. So it is not a matter of the supplier.
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Old 8th March 2021, 08:45 AM   #1605
aniko71 is offline aniko71  Greece
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Default PCBs

Are there any more PCB kits for this project?
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Old 8th March 2021, 05:18 PM   #1606
Hicoco is offline Hicoco  France
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Doug Self Preamp from Linear Audio #5
Question for Doug Self...
Is that possible to change the value of the input capacitors (C2 & C4) for less than 47uF. I would like to try polypropylene audio capacitors and 47uf is difficult to find or very expensive.
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Every DIYer need Balanced-Unbalanced Audio Input Selector Module
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Old 25th March 2021, 12:09 AM   #1607
Cyberpup is offline Cyberpup  United States
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In response to the question: "should it be a simple $3 chip driving a graphic module or do we go all out and use a BBB?" I would favor a two step approach. First the $3, and then a BBB design. Integrating microprocessor circuits into a preamp will certainly present challenges, but they are all solvable with proper design work, and the majority of this work is hardware design work, not software work. The BBB (or similar) with a graphics display will mostly be software work, and just how much time does one want to spen on the dark side?
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Old 10th April 2021, 10:35 AM   #1608
rock12 is offline rock12  United States
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Is it possible to use a wall wart power supply at either 15 volts DC or 18 volts I see them out there that claim linear for 15 bucks and up
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Old 10th April 2021, 10:42 AM   #1609
jwilhelm is offline jwilhelm  Canada
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This requires a dual rail supply, +/- 18V.
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Old 10th April 2021, 12:05 PM   #1610
diyralf is offline diyralf
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Quote:
Originally Posted by Hicoco View Post
Question for Doug Self...
Is that possible to change the value of the input capacitors (C2 & C4) for less than 47uF. I would like to try polypropylene audio capacitors and 47uf is difficult to find or very expensive.
Reducing the size of the capacitors increases the risk of distortion and a drop in the low frequencies region. But you only know exactly when you do a measurement with a good audio analyzer.
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